Multichannel rotary joint

ABSTRACT

A multichannel microwave rotary joint composed of a tandem assembly of single channel microwave rotary joints is described wherein the single channel microwave rotary joints at each end of the assembly can be of a conventional design but the intermediate microwave rotary joints are any number of either or both of two types of single channel microwave rotary joint configurations described herein.

States Patent References Cited UNITED STATES PATENTS 11/1940 New House 12/ 1951 [72] Inventor Glenn A.Walters 12900 Camino Del Valle, Poway, Calif. 92064 1,247

2,223,224 333/98 R 2,579,152 Masters..1....r.r.............. 333/98 R 3,281,728 10/1966 Dorne 333/98 R [21 Appl. No. [22] Filed Jan. 7, 1970 [45] Patented Nov. 16, 19711 OTHER REFERENCES Gran Tham, .l. P., Microwave Rotating Joints, tronic Engineering 10-1951. pp. 377- 381 Elec- Primary Examiner- Herman Karl Saalhach Assistant Examiner-Wm. H. Punter [54] MULTICHANNEL ROTARY JOINT 3 Claims, 1 Drawing Fig.

ABSTRACT: A multichannel microwave rotary joint composed of a tandem assembly of single channel microwave rotary joints is described wherein the single channel microwave rotary joints at each end of the assembly can be of a conventional design but the intermediate microwave rotary joints are any number of either or both of two types of single channel microwave rotary joint configurations described herein.

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MULTICHANNEL ROTARY JOINT This invention relates to a radiofrequency rotary joint, particularly where multichannel operation is required.

In radar practice it is often necessary to rotate or oscillate an antenna relative to associate apparatus. To allow for relative movement between the antenna and apparatus a rotary joint is sometimes necessary. in certain applications, two or more RF transmission lines operating at the same or different frequencies are required to pass through a rotational axis. The main object of the present invention is to provide a multichannel rotary joint consisting of a tandem assembly of single channel rotary joints wherein one set of transmission line terminations are centrally routed and a second set of corresponding transmission line terminations are circumferentially arranged around the central axis and free to rotate. Within the concepts of the invention both coaxial and waveguide terminations are applicable. Proper impedance match, low VSWR, is maintained during rotation. Electrical continuity through the mechanically rotating part is provided by either contacting rings or noncontacting resonant choke sections. The joints are capable of being operated unpressurized or, by the addition of appropriate seals, pressurized.

Various other objects will be apparent from the following description taken in connection with the accompanying drawing wherein;

The single FIGURE is an isometric view of a four channel rotary joint assembly. The particular embodiment of the invention disclosed in the drawing consists of two centrally located single channel rotary joints, one having coaxial transmission line terminations and the second waveguide termina tion, between two conventional rotary joints. Additional rotary joints similar to either or both of the central units can be arranged in tandem to provide additional radio frequency channels. This particular description is not intended to limit the invention as to the number of channels provided by either technique or number of rotary joints employed.

Referring to the accompanying drawing, embodying the concepts of the present invention, comprising four radio frequency joints arranged in tandem having inputs at l, 2, 3, and 4 connecting to single channel rotary joints, 5, 6, 7, and 8 terminating in corresponding transmission lines 9, l0, 1], and 12 respectively. Rotary joint is a conventional design utilizing waveguide to coax input and output transformer sections and a circularly symetric, TEM mode, coaxial section with noncontacting choke joints to maintain electrical continuity while allowing mechanical rotation. Similarly rotary joint 8 is a conventional design utilizing a continuous coaxial transmission line in which contacting ring joints are used to maintain electrical continuity and allow mechanical rotation. This invention relates to the two centrally located single channel rotary joint used in various combinations with similar or other type joints in a tandem assembly.

Rotary joint 6 is one configuration for an intermediate single channel rotary joint in a multichannel assembly. The associate waveguide 2 terminates in a conventional waveguide to coax transformer section and connects to coaxial transmission line 13. The rotary joint consists of: an input terminal wherein coaxial transmission line 13 connects to a double stub (14 and 15) transformer section; an inner conductor, the outer diameter of the portion of central tube 16 between input and output terminations of the rotary joint; an output termination consisting of a coax to waveguide transformer section 17; the outer conductor 18 and noncontacting choke couplings 19-20 and 21-22.

Stub lines 14 and 15 provide an impedance match between the input coaxial line and the coaxial rotary joint circuit, elec trically isolates center conductor 16 from ground and provides an electrical transformation effectively connecting the center conductor of input coaxial cable 13 to the center conductor of the coaxial rotary joint 6. A coax to waveguide transformer section at the output terminal provides the proper impedance match between the coax and waveguide transmission lines. The output section is free to rotate around the central tube. The required mechanical freedom is provided by two noncontacting choke sections. The first consists of plane flange 23 in combination with choke flange 24 containing radial choke line 21 and coaxial choke line 22, each a: quarter wave electrical length. The second consists of central tube 16 and a circumferential path within transformer section 17, which forms coaxial choke line 19 and radial choke line 20 each a quarter wave in electrical length. The rotary section is mechanically supported by bearings 42 and 25. In this presentation the output transmission line 10 is a waveguide transmission line. A two step transformer section 17 provides the proper impedance match for the coax to waveguide transition. An alternate arrangement, utilizing similar transformer sections for electrical isolation of the center conductor and impedance matching can be used to provide for a coaxial line termination.

Rotary joint 7 is a second configuration for an intermediate single channel rotary joint in a multichannel assembly comprised of two coaxial lines connected in parallel wherein the outer diameter of coaxial transmission. line 4 is the inner conductor and the inner diameter of intermediate tube 2627 is the outer conductor of the innermost coaxial line. The outer diameter of the intermediate tube 26-27 is the inner conduc tor and the inner diameter of conductor 40 is the outer conductor of the outemiost coaxial line. This double coaxial line arrangement provides three important functions. The central conductor is at ground potential allowing for the passage of additional coaxial transmission lines through its inner diameter. The intermediate tube is the above ground conductor, supported by insulating sections 44 and 45, and it circumscribes the central conductor, thereby allowing rotation between the input and output sections without the involvement of other transmission lines; and third, the outer c0nductor surrounding the above ground conductor operates at ground potential and prevents RF radiation.

Transmission line 3 is brought through central tube 16, grounds to endplate 28 and has its center conductor connected to intermediate tube 27. This section of the intermediate tube can rotate relative to its other section 26. Elec trical continuity is maintained by conducting ring 29. This ring is cut radially at two or more positions and the resulting sections held together by circumferential spring 30. The ends of intermediate tube 26 and 27, and the associate innner diameters of ring 29 are bevelled such that the radial pressure of spring 30 keeps all parts in good contact with one another. The output coaxial transmission line is grounded to endplate 31 and has its center conductor connected to intermediate tube 26.

Two additional contacting type rotary joints are required in the ground circuit to allow mechanical rotation. One is situated between endplate 31 and the central coaxial transmission line 4. The second mounts within the outer conductor 40 and provides for electrical continuity to endplate 28. In the first case conducting ring 32 is a three piece conical section which is free to slide and rotate on the outer surface of central coaxial transmission line 4. Electrical contact between this conductor and endplate 31 is maintained by the loading of spring 33. In the second case conducting ring 34 is held in contact with inner conductor 40 by means of a series of circumferential tang springs 43. These springs are formed by thinning the metal in the ring mounting area and cutting a series of short longitudinal slots around the circumference and then slightly displacing the tangs so formed in a radial direction. Conducting ring 34 is held in electrical contact with the outer conductor 40 by virtue of the radial spring pressure so afforded. The conducting ring can only move longitudinally relative to the outer conductor. It is spring loaded against endplate 28 by three or more springs, refer item 35. Mechanical rotation occurs between ring 34 and endplate 28. The rotating parts are mounted to the fixed parts through bearings 36, 42, and 25.

Electrical continuity is optimized by utilizing precious metal and/or graphite combinations such as silver-graphite rings on silver surfaces etc. Spring loading assures good electrical contact with wear or small variations in mechanical tolerance. As described the rotating surfaces are of a contacting type. It is apparent to those skilled in the art that noncontacting choke joints of various varieties can be utilized. Contacting types have advantages where large frequency band widths are involved, example multioctave operation. or low frequency transmission is required. While noncontacting choke joints are restricted in their operational band width or too large at low frequencies they have advantages relative to RF noise generation, life, torque, etc.

Where high frequency operation is required the central coaxial transmission line 4 may be of insufficient size to reliably transmit the torque required to drive rotary joint 8. The output section of rotary joint 8 including terminating transmission line 12 is, as are the other terminating transmission line 9, l0, and 11, affixed to output structure of the multichannel rotary joint input assembly associated with end plate 31 and rotates relative to its input section including central coaxial transmission line 4. Drive torque required to rotate rotary joint 8 is transferred through gears consisting of spur gear 38 mechanically attached to the input structure, end plate 28, coupled via end pinion 46 through pinion shaft 39 to opposite end pinion 47 meshed with spur gear 41 which is mechanically attached to the input section of rotary joint 8. The pinion shaft 39 is journaled within the output structure 31 and thereby moves with the 'relative motion of the input and output sections of the rotary joint assembly. The gear and pinion arrangement provide unity coupling; thus, spur gear 41 maintains a fixed angular position with spur gear 38 independent of relative motion between the input and output sections of the rotary joint.

Terminal transmission lines 9, l0, and 11, are radially displaced around the single channel rotary joint assemblies so that continuous rotation, without interference, is allowed. It is apparent that additional joints of types 6 and 7 can be added around central element 16 to increase the number of channels.

Having thus described my invention, what I claim and desire to secure by letters of patent is:

l. A multichannel radiofrequency rotary joint assembly comprising a central tube containing several transmission lines routed in a progressive manner through said tube to coaxially arranged single channel rotary joints positioned in tandem along said tube, wherein one or more of the single channel rotary joints consists of: three concentric conductors comprising two coaxial lines connected in parallel wherein the outer diameter of the central conductor, containing one or more coaxial transmitting circuits, and the inner diameter of an intermediate tube are concentric conductors to form the innermost coaxial line and the outer diameter of the intermediate tube and the inner diameter of the outer conductor are concentric conductors to form the outermost coaxial line; the innermost and outermost conductors connect through end plates to ground; the intermediate tube is electrically isolated and carries the RF energy from the center conductor of the input coaxial transmission line to the center conductor of the output coaxial transmission line; the intermediate tube contains a rotating ring connection to provide electrical continuity while allowing for mechanical rotation; the outermost conductor contains a similar rotating connection; one end plate contains a similar rotating assembly for connection to the central tube; wherein the outer coaxial termination is free to rotate about the central termination.

2. A multichannel radiofrequency rotary joint assembly as described in claim 1 wherein the central conductor is of insufficient diameter to reliably transmit drive torque to the next tandemly positioned end rotary joint and the drive torque is transferred from the input structure of the multichannel rotary joint input assembly by spur gear affixed thereto, which is unity coupled through a pinion shaft journaled in output structure of the multichannel rotary joint assembly, to a spur gear affixed to the input section of the end joint such that by virtue of said gear coupling the input structure of the multichannel rotary joint assembly and the input section of the end joint rotate in unison.

3. A mult|channel radiofrequency rotating oint assembly comprising a central tube containing several transmission lines routed in a progressive manner through the central tube to coaxially arranged single-channel rotary joints positioned in tandem along the central tube, wherein one or more of the single channel rotary joints is comprised of two concentric conductors to form a section of coaxial transmission line consisting of: the outer diameter of the central tube and inner diameter of an outer conductor; end terminals containing choke sections which electrically insolates that portion of the central tube within the rotary joint for operation above ground; and input transformer section at one terminal that matches the impedance characteristic of a coaxial transmission line to the impedance characteristics of the coaxial rotary joint section; and output transformer section at the opposite terminal that matches the characteristic impedance of the coaxial rotary joint section to a waveguide transmission line; a noncontactin g choke coupling between the central tube and the output transformer section to provide electrical continuity and allow mechanical rotation between the central tube and the output transformer section; and a second noncontacting choke coupling in the outer conductor to provide electrical continuity and allow mechanical rotation between terminating halves of the outer conductor, wherein the output transmission line is free to rotate about the central tube. 

1. A multichannel radiofrequency rotary joint assembly comprising a central tube containing several transmission lines routed in a progressive manner through said tube to coaxially arranged single channel rotary joints positioned in tandem alonG said tube, wherein one or more of the single channel rotary joints consists of: three concentric conductors comprising two coaxial lines connected in parallel wherein the outer diameter of the central conductor, containing one or more coaxial transmitting circuits, and the inner diameter of an intermediate tube are concentric conductors to form the innermost coaxial line and the outer diameter of the intermediate tube and the inner diameter of the outer conductor are concentric conductors to form the outermost coaxial line; the innermost and outermost conductors connect through end plates to ground; the intermediate tube is electrically isolated and carries the RF energy from the center conductor of the input coaxial transmission line to the center conductor of the output coaxial transmission line; the intermediate tube contains a rotating ring connection to provide electrical continuity while allowing for mechanical rotation; the outermost conductor contains a similar rotating connection; one end plate contains a similar rotating assembly for connection to the central tube; wherein the outer coaxial termination is free to rotate about the central termination.
 2. A multichannel radiofrequency rotary joint assembly as described in claim 1 wherein the central conductor is of insufficient diameter to reliably transmit drive torque to the next tandemly positioned end rotary joint and the drive torque is transferred from the input structure of the multichannel rotary joint input assembly by spur gear affixed thereto, which is unity coupled through a pinion shaft journaled in output structure of the multichannel rotary joint assembly, to a spur gear affixed to the input section of the end joint such that by virtue of said gear coupling the input structure of the multichannel rotary joint assembly and the input section of the end joint rotate in unison.
 3. A multichannel radiofrequency rotating joint assembly comprising a central tube containing several transmission lines routed in a progressive manner through the central tube to coaxially arranged single-channel rotary joints positioned in tandem along the central tube, wherein one or more of the single channel rotary joints is comprised of two concentric conductors to form a section of coaxial transmission line consisting of: the outer diameter of the central tube and inner diameter of an outer conductor; end terminals containing choke sections which electrically isolates that portion of the central tube within the rotary joint for operation above ground; and input transformer section at one terminal that matches the impedance characteristic of a coaxial transmission line to the impedance characteristics of the coaxial rotary joint section; and output transformer section at the opposite terminal that matches the characteristic impedance of the coaxial rotary joint section to a waveguide transmission line; a noncontacting choke coupling between the central tube and the output transformer section to provide electrical continuity and allow mechanical rotation between the central tube and the output transformer section; and a second noncontacting choke coupling in the outer conductor to provide electrical continuity and allow mechanical rotation between terminating halves of the outer conductor, wherein the output transmission line is free to rotate about the central tube. 